Question: What has four legs, breathes, but doesn't move?
Answer: A baby koala. Baby koalas will cling to their mother when they are first born, depending on their mother to carry them where they need to go or provide them with any other comfort and protection against predators.
Question: I move faster in certain solids, but slower in certain gases. I am typically broken by objects with large masses. I can be used as for pleasure, practice, and even an alarm. If used excessively, I can cause harm. What am I?